Field studies were conducted to determine the effects of various barnyardgrass populations on growth, yield, and nutrient concentration of transplanted “Jetstar’ tomato. Barnyardgrass densities at 16, 32, and 64 plants/m tomato row were tested in 1982 and 1983. Barnyardgrass shoot fresh weights/unit area increased as density increased. Fresh weight of barnyardgrass shoots ranged from 17 100 kg/ha at 16 plants/m of row to 35 500 kg/ha at 64 plants/m of row. At the vegetative stage, tomato shoot dry weight was unaffected by barnyardgrass. As crop growth progressed, tomato shoot dry weight decreased at all barnyardgrass densities. Season-long interference of barnyardgrass reduced marketable tomato fruit number and fruit weight at all densities compared to weed-free plots. Reductions in marketable fruit weight ranged from 26% to 16 plants/m row to 84% at 64 plants/m row. In 1982, concentrations of N, P, K, Ca, and Mg in tomato shoots were unaffected by season-long interference of barnyardgrass at all densities. However, in 1983, concentrations of N and K decreased and concentration of P increased in tomato leaves as the density of barnyardgrass increased. Concentrations of Ca and Mg in tomato leaves were unaltered by barnyardgrass density.

Previous evidence with English beginning readers suggests that some orthographic effects, such as the orthographic neighborhood density effects, could be stronger for children than for adults. Particularly, children respond more accurately to words with many orthographic neighbors than to words with few neighbors. The magnitude of the effects for children is much higher than for adults, and some researchers have proposed that these effects could be progressively modulated according to reading expertise. The present paper explores in depth how children from 1st to 6th grade perform a lexical decision with words that are from dense or sparse orthographic neighborhoods, attending not only to accuracy measures, but also to response latencies, through a computer-controlled task. Our results reveal that children (like adults) show clear neighborhood density effects, and that these effects do not seem to depend on reading expertise. Contrarily to previous claims, the present work shows that orthographic neighborhood effects are not progressively modulated by reading skill. Further, these data strongly support the idea of a general language-independent preference for using the lexical route instead of grapheme-to-phoneme conversions, even in beginning readers. The implications of these results for developmental models in reading and for models in visual word recognition and orthographic encoding are discussed.